lib/libc/stdlib/tdelete.c

   1 /*
   2  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
   3  * the AT&T man page says.
   4  *
   5  * The node_t structure is for internal use only, lint doesn't grok it.
   6  *
   7  * Written by reading the System V Interface Definition, not the code.
   8  *
   9  * Totally public domain.
  10  *
  11  * $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
  12  * $FreeBSD: src/lib/libc/stdlib/tdelete.c,v 1.1.2.1 2000/08/17 07:38:39 jhb Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tdelete.c,v 1.2 2003/06/17 04:26:46 dillon Exp $
  14  */
  15
  16 #include <sys/cdefs.h>
  17
  18 #include <assert.h>
  19 #define _SEARCH_PRIVATE
  20 #include <search.h>
  21 #include <stdlib.h>
  22
  23
  24 /* delete node with given key */
  25 void *
  26 tdelete(vkey, vrootp, compar)
  27         const void *vkey;       /* key to be deleted */
  28         void      **vrootp;     /* address of the root of tree */
  29         int       (*compar) __P((const void *, const void *));
  30 {
  31         node_t **rootp = (node_t **)vrootp;
  32         node_t *p, *q, *r;
  33         int  cmp;
  34
  35         if (rootp == NULL || (p = *rootp) == NULL)
  36                 return NULL;
  37
  38         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  39                 p = *rootp;
  40                 rootp = (cmp < 0) ?
  41                     &(*rootp)->llink :          /* follow llink branch */
  42                     &(*rootp)->rlink;           /* follow rlink branch */
  43                 if (*rootp == NULL)
  44                         return NULL;            /* key not found */
  45         }
  46         r = (*rootp)->rlink;                    /* D1: */
  47         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  48                 q = r;
  49         else if (r != NULL) {                   /* Right link is NULL? */
  50                 if (r->llink == NULL) {         /* D2: Find successor */
  51                         r->llink = q;
  52                         q = r;
  53                 } else {                        /* D3: Find NULL link */
  54                         for (q = r->llink; q->llink != NULL; q = r->llink)
  55                                 r = q;
  56                         r->llink = q->rlink;
  57                         q->llink = (*rootp)->llink;
  58                         q->rlink = (*rootp)->rlink;
  59                 }
  60         }
  61         free(*rootp);                           /* D4: Free node */
  62         *rootp = q;                             /* link parent to new node */
  63         return p;
  64 }